Sensitive relay



c. P. F'SHER SE ITIVE RELAY Aug. 5

Fil May 27, 1944 CZ I eLE-S MI I M 8 m ATTORNEYS Patented Aug. 5, 1947 SENSITIVE RELAY Charles P. Fisher, Boston, Mass., assignor to Sigma Instruments, Incorporated, a corporation of Massachusetts Application May 27, 1944, Serial No. 537,677

16 Claims. 1

This invention relates to electrical relays and is more particularly directed to relays of the type commonly referred to as sensitive relays, which are responsive to small variations in current or voltage.

A primary object of the invention is to provide a relay of this character which shall possess a high degree of sensitivity, with light weight, and with ability to withstand shocks, vibration and variable temperature conditions.

Many relays of this character are required for use upon airplanes, and for various military purposes, where they may be subject to violent physical shocks and also where a great variety of temperature conditions may be met with, and the invention is particularly applicable to relays for use under such severe conditions.

Under some conditions it is desirable to provide a relay of the character referred to which will respond to small changes from a normal voltage although subjected to extreme changes in atmospheric temperature. Such changes in temperature result in large variations in the internal resistance of the coils of the relay and thereby result in great variations in the current flow. If under these conditions it is desirable to make the relay sensitive to small changes from a predetermined voltage, it is necessary to compensate for the variations in pulling force of the magnet due to the variations in resistance and current flow.

It is an object of my invention to provide means for compensating for such temperature changes by varying the biasing force opposing movement of the movable element of the relay in proportion to the temperature. The temperature compensation feature of my invention may be employed in connection with any suitable relay construction, whether embodying the other features of my invention or not. Also the general constructional features of my improved relay may be employed either with or without the temperature compensation feature thereof.

In the accompanying drawings, in which is illustrated one preferred embodiment of my invention,

Figure l is a perspective view of a relay;

Figure 2 is a transverse section on the line 2-4 of Figure 1;

Figure 3 is a vertical section on the line 3-3 of Figure 2;

Figure 4 is a similar section of a part of the relay taken on line 4-4 of Figure 1; and

Figure 5 is a perspective view of a frame elemeat.

Referring to the drawings in detail, the relay comprises one or more coils of insulated wire l0, two coils being shown in the example illustrated. These coils are mounted on cores II which are carried between the arms l2 and M of a frame member or yoke l6. Each core has a head l8 at one end which constitutes a pole piece, this head resting upon the yoke arm l2 while the other end of the core is securely anchored to the yoke arm I 4. In the construction shown the end of the core passes through holes in the yoke arm I4 and in a heel piece l9 which bears against the same and is headed over as indicated at 2|].

In the construction shown, two coils are used. There are, of course, two cores ll each passing through a hole in each arm. The frame or yoke I6 is secured to a supporting member or base 22 which may conveniently be formed in a sort of I-beam shape, as clearly shown in Figs. 2 and 5. The member 22 may be made of any suitable nonmagnetic material such as aluminum. The frame IB is also made of non-magnetic metal. The heel piece I9 is of magnetic material.

The frame [6 is preferably formed so that the arms I2 and M if unrestrained would be spaced apart a distance slightly greater than the distance between the heads l8 and the heel piece l9 resting against the heads 20 of the cores. When the parts are assembled by heading over the cores at 20, this forces in the arm M, which, owing to the resiliency of the metal, is placed under elastic stress. This results in the heads l8 being drawn and held tightly against the arm l2 and this condition will obtain even though the relay is subjected to considerable changes in temperature, or to substantial shocks.

The yoke or frame member IE is firmly fixed to the I-beam member 22 in any suitable manner, as by a pair of screws 24 and 25. The arm I2 is also firmly secured against the end of the I-beam member, as for instance by a screw 26. By this construction the frame and the arm l2 are rigidly I'ixed with relation to the I-beam or base member 22. The arm it, however, is not attached to the end of the I-beam member, so that it is free to exercise its resilient action within the limits permitted by the head 20 on the core. The result is that the head It is always drawn and held firmly against the arm l2 which is fixed in its relation to the base 22. The frame member l6 carries a back plate 30 which is preferably formed integrally therewith by bending a flange along the edge thereof. At the other side of the frame member 16 an ear 32 is provided which is also preferably formed integrally with the frame by bending up a portion thereof.

Mounted in the back plate 30 and ear 32 are a pair of bearing screws 34 between which are pivoted the pivots 36 for the armature carrying arm 40. In the construction shown the armature carrying arm 40 is provided with integral lateral projections 42, the ends of which are shaped to form the conical pivots 36. These are received in cup-shaped cavities in the bearing screws 34. 44 is the armature which lies in proximity to the heads I8 constituting the pole pieces. In the particular construction illustrated the armature is shown as having a slot 46 formed therein, through which the end 48 of the armature carrying lever 40 projects, a portion 50 of the armature being offset and fitting under the lever member 48 to which it is secured in any suitable manner as by means of solder.

The opposite end of the armature carrying lever is bent outwardly to form a contact head 52 which has limited movement between a pair of contact screws 54. These are mounted in brackets 58 to which are joined electrical connectors 58. The brackets 56 are insulated from the frame of the relay, but are firmly mounted in fixed mechanical relationship therewith. In

. the construction shown, this is accomplished by attaching a piece of rigid insulating material 50 to the back plate 30 of the frame, and firmly fixing the brackets 56 to this plate or block of insulating material. The brackets are preferably mounted close to the relay frame so that the width of insulating material 60 between the brackets and the back plate 30 is small. Thus variations in the position of the brackets due to expansion or contraction, or possible warpage of the insulating block, are held to a minimum.

It is to be noted that the bearing screws 34 are mounted in parts rigidly fixed with relation to the frame member l6, preferably by being formed integrally therewith. Furthermore the pivotal axis for the armature carrying lever which corresponds with the axis of the screws 34 is located as close to the end of the frame It carrying the arm l2 as possible. This is important because as before stated the heads l8 that constitute the pole pieces are maintained in fixed relationship with the arm I! and if the pivotal axis is also close to the arm I2 there is little chance for relative displacement between the axis and the surfaces of the pole pieces due either to vibration or expansion or contraction. The result is that the armature is accurately located at all times with respect to the pole pieces, and its range of movement closely defined. The armatureis preferably made of light weight which permits the armature carrying lever to be made light, and thus the whole moving system is light. This is very important in enabling the relay to withstand shocks as the inertia of the moving parts is low and therefore the pivots are subjected to little stress, As the contact screws 54 are firmly mounted in fixed position with relation to the frame member iii, the relationship between the contact screws and the armature carrying lever is also closely controlled so that satisfactory making and breaking of contact may be secured with very limited movement of the armature and lever, and so that the limits of suchmotion, governing values of operating current, are precisely maintained.

The movable armature assembly comprising the armature, the armature lever and the contact head thereon, is preferably substantially balanced in weight about the axis of pivots 38. This may be readily accomplished where the armature may be made of relatively light weight, as in the construction described. The balanced condition may be achieved without adding large counterweights, which would render the whole moving system heavy. with attendant disadvantages of excess weight. The balanced armature system is a valuable feature, particularly in an instrument subject to vibration and shock, as it prevents the conversion of bodily acceleration of the instrument to displacing torque in the armature. Because the moving system is balanced, therefore vibration does not tend to cause chattering at the contacts.

A flexible connector, which may be in the form of a coil spring 62, is used to conduct current from the frame of the relay to the lever 40, the head 52 of which will contact one or the other of the contact screws 54 thus establishing the path of the current. The current may be brought to the frame of the relay and the coils in any suitable manner as by means of a pair of terminals 88 mounted on the insulating block 68 which is secured to the frame IS. The spring 62 may be tensioned so as to constitute a part of or the entire spring loading resistance to movement of the armature lever, or if other spring loading means are provided, as hereinafter described, the spring 62 may be untensioned so that it acts merely as a flexible conductor. Obviously any suitable arrangement of circuits and electrical connections may be utilized.

The construction described provides a relay which is very eiiicient, has a high sensitivity factor, and in which the important mechanical relationships, namely those between the armature and pole pieces and between the contact head on the armature lever and the contact screws are accurately maintained under conditions of shock, vibration and temperature change. The lightnes of the moving system is also of great importance in enabling the relay to withstand shock. The features of construction so far described may be used with or without the temperature compensating features to be now described.

Where the sensitive relay is used under vary ing temperature conditions and it is desired to have the relay respond to variations of voltage from a predetermined norm, it is desirable to provide a temperature compensated biasing resistance to the movements of the armature. In the example illustrated, this is accomplished by providing a bimetallic biasing spring 10. This spring is shown as coiled in the form of a scroll having its inner end fixed to a supporting stud I! which is mounted on the screw 25 which secures the frame to the I-beam support 22.

The other end of the bimetallic scroll I0 is secured by means of a light tension link I5 to a perforated bar 18 forming part of a bracket secured to the contact head 52 on the end of the armature lever. The biasing spring 10 thus. through the link 16, pulls on the armature lever in a direction to opp se the movement of the latter caused by the electromagnetic pull upon the armature. As the pull upon the armature will vary with the amount of current flowing, and as this will vary with the resistance of the coils, and therefore be affected by changes of temperature, this variation will be compensated for by the amount of biasing force exerted by the spring 10. Owing to the bimetallic nature of this spring, it will try to coil or uncoil more or less with variations in temperature, thereby varying the tension upon the armature lever. Compensation may thus be secured so that the biasing force will vary in accordance with change in current flow due to varying resistance, the voltage remaining constant or substantially constant. Slight departures from the voltage norm will therefore result in opening and closing of the relay irrespective of external temperature conditions.

Any suitable adjusting means for the biasing effect may be utilized such as by providing a plurality of perforations 82 in the bar 18. The end of the link 16 may be hooked into any selected perforation thereby varying the angularlty of the link and consequently the effective length thereof and direction in which the force is applied. Any other suitabl adjusting means may obviously be employed.

The tension of the biasing spring may constitute the entire biasing force upon the armature' lever or its action may be combined with a biasing force produced by the spring 62 as may be found most desirable.

As above stated, the thermostatic compensating means described may be used with the particular construction of relay herein set forth, or with any other suitable construction of relay.

While I have illustrated and described in detail certain preferred forms of my invention, it is to be understood that changes may be made therein and the invention embodied in other structures. I do not, therefore, desire to limit myself to the specific constructions illustrated, but intend to cover my invention :broadly in whatever form its principle may be utilized.

What is claimed is:

1. A relay comprising a metal frame member having resilient magnet carrying arms thereon, a coil mounted between said-arms and a core for said coil connecting said arms and holding them in such relative position that they are normally under resilient stress, one end of said core forming a pole piece which is held in definite relationship to one of said arms by the resilient stress of the other arm.

2. In a relay, a base member, a fram member secured thereto having two arms located at opposite ends of said base member, one of said arms being rigidly secured to an end of said base member, the other arm being resilient and free from direct fixed connection to the base member, a magnet core connecting said arms and holding the resilient arm under resilient stress, said core having a pole piece thereon located in fixed position with respect to the arm which is fixed to th end of the base, and an electromagnetic coil surrounding said core.

3. In a relay, a base member, a frame member secured thereto having two arms located at opposite ends of said base member, one of said arms being rigidly secured to an end of said base member, the other arm being resilient and free from direct fixed connection to the base member, a magnet core connecting said arms and holding the resilient arm under resilient stress, said core having the pole piece thereon located in fixed position with respect to the arm which is fixed to the end of the base, an electromagnetic coil surrounding said core, said frame member carrying pivot bearings, an armature lever mounted in said pivot bearings, and an armature carried by said lever in juxtaposition to said pole piece.

4. In a relay, a base member, a frame memher secured thereto having two arms located at opposite ends of said base member, one of said arms being rigidly secured to an end of said base member, the other arm being resilient and free from direct fixed connection to the base member, a magnetic core connecting said arms and holding the resilient arm under resilient stress, said core having..a pole piece thereon located in fixed position with respect to the arm which is fixed to the end of the base, an electromagnetic coil surrounding said core, said frame having members carrying pivot bearings located close to the end of the frame carrying the arm which is secured to the base member, an armature lever pivoted in said bearings and an armature carried by said lever adjacent to said pole piece.

5. In a relay, a frame member comprising an integral metal piece having arms bent therefrom in one direction, and having bearing supporting members bent therefrom in the opposite direction, bearings carried by said members, an electromagnet carried by said arms; an armature lever pivotally supported in said bearings, and an armature on said lever cooperating with said electromagnet.

6. In a relay, a frame member comprising an integral metal piece having arms bent therefrom in one direction, and having bearing supporting members bent therefrom in the opposite direction, bearings carried by said members, an electromagnet carried by said arms, an armature lever pivotally supported in said bearings, and an armature on said lever cooperating with said electromagnet, said electromagnet including a core having a pole piece adjacent to the end of the frame member nearest to the pole piece.

7. In a relay, a frame member comprising an integral metal piece having arms bent therefrom in one direction, and having bearing supporting members bent therefrom in the opposite direction, bearings carried by said members, an electromagnet carried by said arms, an armature lever pivotally supported in said bearings, and an armature on said lever cooperating with said electromagnet, one of said bearing supporting members carrying contact screws for contacting the armature lever.

8. In a relay, a frame member comprising an integral metal piece having arms bent therefrom in one direction, and having bearing supporting members bent therefrom in the opposite direction, bearings carried by said members, an electromagnet carried by said arms, an armature lever pivotally supported in said bearings, and an armature on said lever cooperating with said electromagnet, one of said bearing supporting members having a rigid block of insulating material fixed thereto, brackets fixed to said insulating block and contact screws carried by said brackets and adapted to engage the end of said armature lever.

9. In a relay, a frame member having an electromagnet supported thereon and having bearing supporting members bent therefrom, bearings in said bearing supporting members, an armature lever pivotally supported in said bearings, an armature on said lever cooperating with said electromagnet, an insulating block rigidly secured to one of said bearing supporting members, contact carrying members mounted on said insulating block, and contacts carried by said contact carrying members and adapted to contact with opposite sides of said armature lever.

10. In a relay, 9. base member of generally I- beam shaped section, a frame member secured to the face on one of the I-beam heads, said frame member having arms bent therefrom and located adjacent to the ends of the I-beam member, means for securing one of said arms rigidly to the end of said I-beam member, the other arm of said frame member being free from direct fixed connection with said I-beam member, a pair of cores carried by said arms andextending one on each side of said I-beam member, electromagnetic coils carried by said core and received in the side recesses of said I-beam member, bearings carried by said frame member, an armature lever pivotally mounted in said bearings, and an armature carried by said lever and cooperating with said electromagnetic coils.

11. In a relay. a frame having arms projecting therefrom in one direction, an electromagnet carried by said arms, bearing supporting members projecting from said frame in the opposite direction from said arms, bearings carried by said bearing supporting members, an armature lever pivotally mounted in said bearings and having an armature at one end thereof cooperating with said electromagnet, contact members carried by said frame, the other end of said armature lever extending between said contact members and forming a contact element for engagement therewith, said armature lever and armature being substantially balanced in mass about the axis of pivotal support of said lever.

12. In a relay, a frame, an electromagnet carried thereby, an armature lever pivotally supported on said frame, an armature carried by said lever and cooperating with said electromagnet, a biasing spring in the form of a bi-metallic coil supported on said frame, a bracket connected to said armature lever provided with means for connecting a link thereto in a variety of positions, and a link connecting said bracket to said bimetallic spring.

13. In a rel y, 2. frame having resilient magnet carrying arms thereon, a magnet coil mounted between said arms, a core for said coil connecting said arms and holding them in such relative position that they are normally under resilient stress, one end of said core forming a pole piece which is held in definite relationship to one of said arms by the resilient stress of the other arm, bearing supporting members mounted on said frame, bearings mounted in said members, an armature lever pivotally mounted in said bearings, an armature carried by said lever cooperating with said pole piece, a spring carried by said frame, and connected with the armature lever, and contact members cooperating with said armature lever and rigidly mounted upon, but in sulated from said frame.

14. An electromagnet comprising a metal frame member having magnet carrying arms thereon, a coil mounted between said arms, and a core for said coil connecting said arms, said core being of a length less than the distance between said arms before the core is attached thereto by an amount such that when the arms are drawn towards each other by attachment to said core said arms are put under a resilient stress which is maintained as long as the arms are attached to said core, one end of said core forming a pole piece which is held in definite relationship to one of said arms by the resilient stress of the other arm.

15. An electro'magnet comprising a metal frame member including a resilient magnet carrying arm, a coil mounted on said frame member and having one end adjacent to said resilient arm, a core mounted in said coil and secured at one end to said resilient arm, the other end of the core forming a pole piece, means on the frame for supporting said pole piece in fixed position, the connection between the core and said resilient arm holding said resilient arm under stress within the elastic limit of the metal of said arm, so as to cause said arm to apply said stress to said core.

16. In an electromagnet, a coil, a core passing through the coil and terminating in a pole piece, a frame carrying the coil, an armature lever pivotally mounted on the frame, and an armature mounted on said armature lever, said armature having a slot formed therein and a portion adjacent to said slot offset, the end of the armature lever fitting in said slot and the offset portion of the armature fitting under the lever, and means for securing the armature lever and armature together.

CHARLES P. FISHER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,576,768 Loudon Mar. 16, 1926 1,706,042 Radley Mar. 19, 1929 1,960,198 Beetem May 22, 1934 2,037,118 Chubbuck Apr. 14, 1936 834,750 Pusey Oct. 30, 1906 850,205 Bergman Apr. 16, 1907 2,261,887 Menzel Nov. 4, 1941 1,843,351 Wilckens Feb. 2, 1932 

